What is the purpose of the riser in a septic system?

The purpose of the riser in a septic system is to provide access to the septic tank for inspection and pumping. This access point is crucial because it allows septic service professionals to easily reach the tank for maintenance tasks such as pumping out solids and performing inspections to ensure the system is functioning properly. Access through a riser can facilitate more straightforward and efficient servicing, reducing the need for extensive excavation and exposure of other parts of the system.

The other options relate to aspects that do not accurately describe the function of a riser. Increasing the water level, insulating the tank, and filtering incoming waste are features associated with different components or functions of a septic system, but they do not pertain to the role of the riser. Understanding the specific functionality of each part of a septic system is essential for effective maintenance and proper operation.